"While Newton seemed to draw off the veil from some of the mysteries of nature, he showed at the same time the imperfections of the mechanical philosophy; and thereby restored her secrets to that obscurity, in which they ever did and ever will remain." — David Hume 

There is a debate among scientists regarding which is the most fruitful approach to understanding the mysteries of the natural world. The winners of this debate dictate what sort of research questions are likely to be funded at the highest levels, and so where the brightest minds are likely to focus; there is much at stake. On one side are the molecular biologists, among them was James Watson, who along with Francis Crick and Rosalind Franklin first discovered the structure of the DNA molecule. On the other side there are the ecologists, people who study organisms, populations, and communities of species, (a.k.a., naturalists). A leader from that side of the debate was E.O. Wilson. Edward O. Wilson and James D. Watson, both Harvard faculty members from 1956 to 1976, had a rivalry over the direction of the university's biology department. Wilson, a two-time Pulitzer Prize winner and biodiversity expert, and Watson, a Nobel laureate and former director of the Human Genome Project, had different views on the future of biology.

As far as Watson was concerned, molecular biology and genetics were the future of biology and organismic biology was irrelevant; “Smart people don't go into ecology.” Ultimately, Watson won, and Harvard University’s Biology Department shed its historical leadership in organismal science for a reductionist focus on molecules. This unfortunate reality is that even with a precise knowledge of how molecules work, it will never yield insights to how species, whole organisms comprised of millions of interacting molecules, might respond to the introduction of invasive weeds, or if or how they might survive modern climate change, or the importance of biodiversity to our future.

There are so many unanswered questions in ecology. Many might seem trivial to Watson and his academic progeny, but some of which may have direct bearing on the future of our planet’s biodiversity. One question I have been pondering recently is egg laying in lizards. Sounds arcane but stick with me. Most animals lay eggs. Arthropods, fish, amphibians, reptiles, birds, and a few mammals all lay eggs. It is the standard reproductive strategy for most animal life on our planet. Except there are exceptions. Most mammals, including us, being the biggest exception, but within reptiles there are exceptions as well.

Rattlesnakes don’t lay eggs, rather they are viviparous, giving birth to free-living “snakelets”, neonates (not hatchlings). For lizards in the arid regions of North America there are a few species of horned lizards, a few species of alligator lizards, and night lizards that are also viviparous, giving birth to neonates, not hatchlings. Most other lizards of our region lay eggs. There are obvious advantages to being viviparous. If you lay eggs, those eggs are subjected to changing weather patterns that might include unseasonable heat, freezes, droughts, and floods, any of which could cause the growing embryos to perish. The eggs might be dug up and consumed by egg predators (snakes, skunks, raccoons, and others), or spoiled by toxic bacteria. Keeping embryos inside the mother’s body avoids these threats. She can move in and out of sunlight to keep her growing embryos at optimal temperatures, do her best to avoid predators and provide a toxic-bacteria free space for her embryos to grow. It makes good sense that those few horned lizards that give birth to neonates, including the greater short-horned lizards, live at the highest elevations and or highest latitudes, from 2,000-10,500 feet. This is higher than any other horned lizards, or any lizard, places where the weather is most variable and freezing temperatures can occur well into the spring. Keeping their embryos protected, ensconced within their bodies until the neonates are ready to live independently, move, and forage, likely means a higher neonate success. These horned lizards can give birth to a clutch of as many as 15-16 neonates, two to three times as many as flat-tailed or desert horned lizards’ egg clutches, though less than the egg clutches of Blainville’s and regal horned lizards. 

The northern latitude – high elevation driver for being viviparous makes good sense, except not all high elevation lizards are viviparous. The southern sagebrush lizards that we see anywhere above 6,000 feet in the San Jacinto, Santa Rosa, and San Bernardino Mountains lay eggs (are oviparous). They can be found as high as 9,000 feet, and within those boundaries they can be abundant. Clearly being an egg layer has not been a handicap. On the Colorado Plateau, plateau fence lizards occur between about 3,000-9,000 feet and lay eggs. Being viviparous is one way to thrive at high elevations, but it is not a requirement. Behavioral adaptations can also be important.

Greater short-horned lizards are one of the few lizard species that can be found in Canada, albeit just barely. One Canadian study tracked these horned lizards using radio transmitters. The researchers found that the lizards selectively dug winter burrows on sites that were most likely to collect the deepest snowdrifts. They entered those burrows long before the first snow fell, apparently having an innate sense of what location would accumulate the most snow in the coming months. It seems counter intuitive, but deep snow insulates the burrow, never allowing the lizard to get below 32˚ F (0˚ C), whereas areas with little or no snow lack insulation and can fall far below freezing. Young lizards that burrowed in areas with little snow cover invariably froze and perished. Watson’s molecules would never have predicted such an adaptation. Perhaps the southern sagebrush lizards and plateau fence lizards have similar behavioral strategies for where they lay eggs and where they winter.

As our climate warms many species will shift to higher elevations. We are seeing that with side-blotched lizards, western fence lizards, and Blainville’s horned lizards. The lizards are tracking their preferred temperatures, but even as those higher elevations are getting warmer, they are getting more variable. Those interlopers from lower elevations may not have the behavioral knowledge to deal with freezing winter and spring temperatures. We just don’t have a frame of reference to predict the unprecedented (from our human perspective) changes that are occurring and will likely continue. Having naturalists out in nature, documenting how species are responding to these changes is more important than ever. Harvard University and those that followed their lead won’t be leading that charge.

Nullius in verba – Go outside, tip your hat to a chuckwalla (and a cactus), and think like a mountain